Have you talked to MoonShadow? I know she'd give you some tips if you asked. Otherwise it sounds to me like you have a good plan going. Like Neptunesmom said, just make sure you are prepared to give them up & ready to handle it when the bettas can't be saved. I have 1 of MoonShadows rescues, and I hope to be able to add more rescued bettas later.

My best advice - be ready to give them up. I decided to rescue a betta and rehome. He is still in the process of getting better (no anal fin), but it is so hard to think of passing him on to another. I keep saying to myself, "but then I can rescue more". But, I needed to realize I am not the type that can easily foster without becoming overly attached.

THIS.

I have 8 cats because I find it hard to give up fosters! Remington, the fish in my avatar, was a rescue I thought I could give up. Nope

If I ever did start a rescue I would do it on the cheap by shopping at thrift stores looking for large-ish glass containers (I'm not fond of plastic) and saving my money for the actual fish, meds and HEATERS. I also would not do it without an ample supply of indian almond leaves. I would not filter the tanks which would mean taking time to do lots of water changes.

I've been thinking about doing something like this too, but how would you know that the fish's new family would take care of him or her?

I hate the thought of rescuing Bettas, just to give them to someone who doesn't even know that they need a heater :(

Make them fill out a questioner. If you adopt a dog or cat from a rescue they make sure you are going to provide properly for them first, so what can't we ask them what size tank the betta will have & what other care they plan on giving? The questions you asked would of course be up to you. You could also type up an info sheet on bettas to send with the fish to there new homes.

I don't have a betta rescue but, if I did I would get a 25-30 gallon tank and some smaller containers to float inside then have the large tank heated so I wouldn't have to buy a bunch of smaller heaters, and I wouldn't have to worry about sterilizing all the heaters after a fish either gets adopted or passes away. I'm not sure if that would work but it is just and idea.

i agree no filters. Daily water changes i do for my rescued , but i keep them in the container they come from the store. I don't have to keep them longer than 2 weeks because i already have people who waiting for them. If you keep them in one gall or 0.5 gall you don't need to do daily water changes. For 0.5 gall you need like every 2 days for 1 gall about every 3-4 days.
Buy aquarium and Epsom salt. Aquarium salt in the pet store and Epsom salt (unscented ) at any pharmacy department should have it.
Do you know how to acclimate them when you do 100% water changes.
Do you need instructions and uses for the salts?
Make sure if you have more than one betta you do not cross contaminate any changing equipment between them. And sometimes you don't even see any symptoms of sickness until later.

But i am thinking when we rescuing sick bettas we left healthy betta on the shelf that will be sick in a week or two if no one buy them. 3 wk ago i saw white beautiful betta that i really want to rescue. I had someone who want a betta because her died and she was afraid to buy sick one. So when i went 3 weeks later i couldn't buy that white one because he didn't look good at all. So i am thinking we buy sick and live healthy one to die.
And when we give you nourish sick one there is more chance for him to get sick again. Then the new owner will end up with sick betta and frustration. I don't know may be i am wrong.
When i buy fish for someone i try to buy healthy one. If i want to rescue sick one that i did before i will do it for myself.

I to am going to start a rescue kinda. The fish will be housed in a 1QT pickle jar until I can eat my way through the 1 gal (lol) and then they can stay there until I find them a home or they will stay there until I get them a better container with me :) The biggest problem is finding homes.